1. Field of the Invention:
The present invention relates to an automatic rim exchanger for use in a tire uniformity machine, which exchanger is adapted to dismount and mount upper and lower rim structures to exchange upper and lower rims for new rims corresponding to the size of a tire to be handled.
2. Description of the Prior Art:
At first, the above-referred tire uniformity machine in the prior art will be described in general with reference to FIGS. 4 and 5. As shown in these figures, an upper spindle 6 and a lower spindle 6' are disposed perpendicular to a roller conveyor 2 provided on a main frame 1 as conveying means for a tire T, and are arranged on the same axis as the axis of the tire T, and the upper spindle 6 is arranged so as to be rotatable by means of a rotary driving device 5 and holds an upper rim 9 at is bottom end.
The lower spindle 6' is supported by an elevator member (piston rod) 8a in an elevator device 8 such as a hydraulic cylinder or the like and holds a lower rim 10 at its top end, and the tire T is mounted between the upper and lower rims 9 and 10. In this state, the upper and lower spindles 6 and 6' are integrally rotatable, and by installing a loading device 3 and a load detecting device 4, a uniformity inspection the tire is carried out in a well-known manner.
Details of the heretofore known structures of the upper and lower spindles 6 and 6' and the upper and lower rims 9 and 10 are shown in FIG. 5. As shown in this figure, the upper rim 9 is fastened by means of bolts 12 to a mounting flange 11 provided at the bottom of the upper spindle 6, while the lower rim 10 is fastened by means of bolts 14 to a mounting flange 13 provided at the top of the lower spindle 6'. In addition, within the upper spindle 6 is formed an air feed passageway 16 for feeding pressurized air into the tire T through a rotary union 15. The lower spindle 6' is rotatably supported within a lower spindle main body 17 by means of a bearing 18. The elevator member 8a of the elevator device 8 is fastened by means of bolts to the spindle main body 17 so that the lower spindle 6' can be freely rotated and elevated or lowered. And in the mounting flange 11 at the bottom of the upper spindle 6 and on the top end of the lower spindle 6' are provided tapered cone-shaped fitting portions 19 and 20, which are engageable with and disengageable from each other in response to vertical movements of the upper and lower spindles 6 and 6'.
In addition, in the aforementioned tire uniformity machine, tire sizes and rim sizes are correlated to each other. Hence, in accordance with a change of tire sizes, exchange operations the upper and lower rims 9 and 10 on the upper and lower spindles 6 and 6' are necessitated. However, the above-described exchange operation includes mounting and dismounting the upper and lower rims 9 and 10 to and from the upper and lower spindles 6 and 6' via bolts 12 and 14, and such necessitates an extremely long time associated with maintaining mounting precisions of the upper and lower rims 9 and 10, and also necessitates skilled manpower. Furthermore, as the rim itself is a considerably heavy body and the working space is relatively narrow, the aforementioned rim exchange work that is executed entirely by hand must occur under a severe working condition.
Automatic rim exchangers for dealing with the aforementioned problems have been already developed and proposed (Laid-Open Japanese Patent Specification No. 60-49930 (1985); Laid-Open Japanese Patent Specification No. 60-76330 (1985)), and these automatic rim exchangers have the structure shown in FIGS. 6 and 7. Instead of the mounting/dismounting structure which detachably mounts the upper and lower rims 9 and 10 to the upper and lower spindles 6 and 6' by bolt fastening means, the upper rim 9 is capable of being automatically mounted and dismounted by providing a lock device 26 or 26a which can be engaged with and disengaged from the upper spindle 6. The lower rim 10 is integrally assembled with the lower spindle 6', but the lower spindle 6' is detachably mounted to the elevator member (piston rod) 8a, thereby allowing the lower rim 10 to be detached. Thus, the upper and lower rims 9 and 10 can be dismounted and mounted to be exchanged. In either one of these known rim exchangers, it is necessary to prepare a plurality of spindle assemblies 50 or 50a that is highly precise and expensive for one tire uniformity machine as shown in FIG. 6. Since the spindle assembly is a considerably heavy body, an exchange unit 60 including that assembly has such a heavy weight that its exchange by humanpower is impossible. And since the tire uniformity machine allows a limited working space, it is necessary to make the exchange unit as light as possible. With regard to further detailed explanation of the structures shown in FIGS. 6 and 7, reference should be made to the above-cited laid-open Japanese patent specifications.
As will be seen from the above description, the automatic rim exchangers for use in a tire uniformity machine in the prior art involve problems in that they necessitated a plurality of spindle assemblies that are highly precise and expensive for exchanging rims, resulting in a very high cost, and in that a plurality of exchange units including the aforementioned spindle assemblies are considerably heavy bodies, and bring about difficulties in the rim mounting/dismounting work within the limited working space of the tire uniformity machine.